Radiation detection devices



May 22, 1956 M. N. FAIRBANK ET AL RADIATION DETECTION DEVICES FiledMarch 28, 1951 5 Sheets-Sheet l FIG. l

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ATTORNEYS May 22, 1956 M. N. FAIRBANK ET AL 2,747,103

RADIATION DETECTION DEVICES Filed March 28, 1951 3 SheetS-Shee 2 50 51|(SI2 450 f f FIG. 5

FIG. 6 @MQ/f6 ATTORNEYS May 22, 1956 M. N. FAIRBANK ET AL RADIATIONDETECTION DEVICES 3 Sheets-Sheet 3 Filed March 28 1951 S 3 9 T l@ N E V9 4 8 LCI Ill y 1 U... m 4 E 7 W l rl G r|. .l 4 I G 7 .F mw .F rr nw f[i1. 3 B 7 rll lllllll 114/@ V|\l\|| rl/.VIL IIN/ .k O fm 8 6 8 7 QTL O OO 2 O O Ww/c7.

ATTORNEY FIG. 9

United States Patent O l' RADil'fIN BETEQTN EVCES Murry N. Fairbanlr,lieimont, Wiliiani Shurciiii,

Cambridge, t/iass., assignors to Poiarn'd Corporation, Cambridge, Mass.,a corporation of vor.

Appunti@ runen 2s, rast, sensi ne. eras-s2 12 creme. ici. rsa1-ra;

tive to nuclear radiation, together with photographic reagents,releasable upon application of pressure to said envelope, for processingsaid photosensitive materials to form a transfer print therefrom on aprint-carrying element located within the envelope, and also whereinsaid envelope includes means for indicating the extent of exposure ofthe dosirneter to the nuclear radiation to be detected.

Other objects of the invention are to provide a dosirneter of thecharacter described wherein the means for indicating the extent ofexposure of the dosirneter to nuclear radiation is a reference stripwhich, at least upon contact with photographic processing reagentswithin the envelope, is capable of providing a scale of gray tonesadapted to be compared with a transfer print of a photosensitiverecording strip to determine the extent to which the recording strip hasbeen subjected to nuclear radiation and may comprise a preexposed andundeveloped photosensitive strip photographically printed through arecord of a scale of gray tones or a strip of substantially insensitivematerial bearing or being provided with a preformed scale of gray tones;to provide in a dosirneter of the character described an unexposedphotosensitive portion capable of indicating possible failure of theunit; to provide in a product of the nature with which this invention isconcerned a photosensitive element comprising at least onephotosensitive recording strip and preferably comprising two or morephotosensitive recording strips of silver halide wherein each recordingstrip has a different film speed with respect to nuclear radiation to bedetected.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the products possessing thefeatures, properties and the relation of f components which areexemplified in the following detailed disclosure, and the scope of theapplication of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawings wherein:

Figure i is a plan View of a dosirneter with the envelope wall portionsthereof spread apart;

Fig. 2 is a sectional View on the line 2-2 of Fig. 1 and shows thedetailed construction of an envelope wall member and a photosensitiveelement carried thereby;

Fig. 3 is a plan View of a sealed dosirneter in storage condition withthe leader or tab portions thereof folded over upon an outer surface ofthe envelope;

Fig. 4 is a sectional elevation on the line 4 4 of Fig. 3;

Fig. 5 is another embodiment of a dosimeter envelope with the wallportions thereof positioned in spread-apart condition;

Fig. 6 is a plan view of a preferred embodiment of a dosirneter with theenvelope wall portions thereof positioned in spread-apart condition asin Fig. l;

Fig. 7 is a sectional view on the line 7-7 of Fig. 6;

Fig. 8 is a sectional view on the line 3--8 of Fig. 6;

Fig. 9 is a diagrammatic plan view of a fan-fold type of dosirneter unitin unfolded condition;

Fig. l0 is a. diagrammatic elevation showing the fanfoid unit of Fig. 9in folded condition;

Fig. ll is a plan view of a device or apparatus for processing,shielding and storing dcsiineters of the character forming the subjectof this invention; and

Fig. l2 is a sectional elevation taken on the line 12-12 of Fig. 11.

By the present invention, means are provided for detecting the presenceof nuclear radiation and for indicating or recording and for measuringthe dosage of radiation to which these means have been subjected.Nuclear radiation as employed herein includes electromagnetic radiationhaving a wavelength shorter than the wavelength of radiation within theultraviolet region of the spectrum, for example X-rays and gamma rays,and also includes corpuscular radiation, for example alpha particles,beta particles, fission product particles and the like. As it is wellknown, all types of nuclear radiation are, at least to some extent,harmful to the human body. X-rays and gamma rays are, in general, themost dangerous types of nuclear radiation. Consequently, a detectiondevice should be designed so as to detect these most harmful types ofradiation. The present invention is particularly concerned with thedetection of radiation lying within a wavelength range of from 0.2 A to0.002 A, it being pointed out that X-rays and gamma rays are bothincluded within this range.

Radiation detection devices, now commonly called dcsimeters, are usefulto laboratory Workers and the like as means for indicating whetherworking conditions are unsafe due to the presence of nuclear radiationin harmful quantities and arising, for example, from devices whichgenerate X-rays or in the handiing, for one purpose or another, ofradioactive materials. Dosimeters are also useful for indicatinglocalities which have become contaminated by nuclear radiation as aresult, for example, of an atomic explosion. Dosimeters, such as thoseof the present invention which are able to record the radiation dosageto which a person has been subjected, possess further utility in thatthey will supply needed information for appropriate medical treatment.

Photosensitive materials, in addition to being sensitive to light, arealso, as a general rule, sensitive to or exposable by nuclear radiation.A photosensitive heavy metal salt, capable upon photoexposure of havingformed therein latent image which is developable to the metal of thesalt to provide a visible image, is an example of such a photosensitivematerial. Preferred materials ernployed in the practice of the inventionare the photosensitive silver halides which are commercialiy availablein a wide variety of photographic emulsions. Recognizing this propertyof photosensitive materials, the present invention utilizes suchmaterials to provide the novel dosirneter set forth herein.

As it is now well understood to the art, a photographic transfer processmay be carried out to provide, in a printcarrying element, a reverseimage of a latent image contained in a layer of a photosensitivematerial. In the case of a photosensitive element having aphotosensitive silver halide layer which contains latent image,processing of this character includes permeating a photographicdeveloper and a silver halide solvent into the photosensitive element,including the silver halide layer, and bringing the photosensitiveelement and the print-receivin g element into face-to-face contact. Theresult of this procedure is to develop latent image to silver and toform in the photosensitive element a soluble silver complex fromunexposed silver halide for transfer to the print-carrying element. Thiscomplex, at least in part, is transferred by imbibition to theprint-carrying element where it is developed to silver to provide thedesired reverse image.

The photosensitive units or dosimeters illustrated herein all make useof the principles of a transfer process in indicating or recording thedetection of nuclear radiation. These principles are specifically setforth in United States Patent No. 2,543,181, issued February 27, 1951 toEdwin H. Land for Photographic Product Comprising a Rupturable ContainerCarrying a Photographic Processing Liquid. This patent also includes adetailed description of film units comprising a photosensitive elementand a printcarrying element and adapted to contain all of thephotographic materials needed to process the unit, and further includesa description of liquid processing compositions usable with such units.The practices, photographic materials and compositions therein describedare generally suitable for carrying out the present invention andspecial reference for the details thereof are made to the just-mentionedpatent.

In all embodiments of the invention herein set forth, the dosimeter orphotosensitive units disclosed comprise an envelope having a pair ofoverlying wall members which are releasably secured together. Withreference to Figs. l through 4, such an envelope is indicated generallyby the reference numeral 10. The overlying wall members of envelope 1t)are similar in outline and may comprise individual elongated layers 11and 12 which are generally rectangular in shape. As illustrated in Fig.4, layers 11 and 12 are positioned in superposed relation so as to formthe outer layers of the envelope 10. Layers 11 and 12 are releasablysecured together by means of a strippable adhesive bond along thelongitudinal edges thereof and also transversely of the layers at oneend thereof. This adhesive bond between the overlying envelope layersalso extends transversely thereof at a position which is preferably,although not necessarily, somewhat removed from the second end of thelayers. This bond is adapted to provide a seal between the layers whichis impervious to liquid and to light of a wavelength actinic tophotosensitive materials Within envelope 1d and is shown in Fig. 3 at 14as extending over an area lying between the rectangular marginal outlineof the envelope as therein illustrated and the dotted line parallel tosaid outline.

By this arrangement it will be apparent that each layer 11 and 12providing an envelope wall member will have a portion thereof at one endwhich is unconnected to the other layer. These portions 16 and 17 (Fig.l) in the form of extensions are in effect leaders which provide meansto facilitate handling of the photosensitive unit, as well as means toassist in stripping the layers so that they may be placed in thespread-apart condition of Fig. l.

Alternatively, the Wall members for the envelope 1@ may be a part of asingle elongated strip which is folded transversely of itself, as forexample on the fold line 151i shown in Fig. 5.

Each of the layers 11 and 12 of the envelope is formed of a materialwhich is substantially impervious to processing liquid employed withinthe unit and which is also substantially impervious to the atmosphere.These layers 11 and 12 are further characterized by the fact that theyare each substantially opaque to light of a wavelength to whichphotosensitive material within the envelope is actinic and that theytransmit shorter wavelength radiation including X-rays and gamma rays.

The envelope 10 is adapted to contain a photosensitive element and aprint-carrying element generally and respectively designated by thereference characters 15 and 18 and a rupturable container Ztl adapted tohold a photographic liquid processing composition. The photosensitiveelement 15 and the print-carrying element 13 are each carried by theinner surface of a dierent one of the layers 11 and 12. For example, thephotosensitive element 15 is shown associated with the layer 11 and theprint-carrying clement 18 is shown associated with the layer 12. Thecontainer 20, which is adapted to hold a liquid processing composition,may be carried by either of the layers 11 or 12 but is generally andpreferably associated with the layer having the print-receiving element13 mounted thereon. Container 20 is provided with a releasably sealedliquid-dispensing mouth located to extend transversely of the layer 12at a position adjacent one end of the print-carrying element 1S.

The photosensitive element l5, the print-carrying element 18, and acontainer 2t) are so positioned on their respective layers 11 and 12that when the layers are superposed, the photosensitive element and theprint-carrying element will be located in superposed registered relationwith the container positioned to discharge its liquid content betweenthe layers so that it may be spread over the opposing faces thereof.Container 20 is So constructed that, upon the application of suitablepressure to opposite sides of the envelope 1d, it may be ruptured todischarge its contents through the dispensing mouth thereof.

The Wall members or outer layers 11 and 12 of the envelope aresubstantially impervious to a liquid processing composition employedwith the dosimeter unit and to this end are constructed to comprise abase 21 formed of kraft paper to which a layer 23 of aluminum or leadfoil is adhered and over which a coating 25 of a thermoplastic materialis applied. The coating 25 may comprise a polyvinyl acetal, for examplepolyvinyl butyral, polyvinyl acetal or polyvinyl formal, and is in eecta pressureand/ or heat-sensitive adhesive. The construction of the outerlayers of the envelope for all embodiments of the invention is shown indetail in Fig. 2.

Use of a plastic coating over the layer 23 of aluminum or lead foil isuseful from a number of standpoints. The coating is selected to be inertto the processing liquid and also as a means for releasably securingtogether the layers 11 and 12 over the area 14 of Fig. 3. Furthermore,the adhesive properties of the coating 25 permit the container Ztl to beadhered thereto. For example, the container may be heat-sealed to thelayer 12 along the edge of the container which is closest to the leader16. Also, if desired, the adhesive properties of the coating 2S may beutilized, as in the dosimeter structure of Fig. 6, for securing thephotosensitive element and the print-carrying element thereof to theinner surfaces of the envelope wail members. To substantially preventthe access of actinic light at the sealed portions of the envelope wallmembers, it is desirable to include a suitable light-opaque dye orpigment such as carbon black in the plastic material forming the coating25.

All of the detection devices disclosed herein have certain commoncharacteristics. For example, each embodiment of the invention makes useof at least one photosensitive recording strip and at least onereference strip which may or may not be of a photosensitive nature. Eachreference strip provides means for indicating the extent of exposure ofthe dosimeter to nuclear radiation and is characterized by the factthat, at least upon contact with the photographic processing reagentswithin the envelope, it is capable of providing a scale of gray tonesadapted to be compared with a transfer print of a recording strip todetermine the extent to which the strip has been subjected to nuclearradiation. In all embodiments of the gramos invention the photosensitiverecording strips and the reference strips are generally rectangular inshape, although of course the invention may be carried out with othergeometrical outlines for these recording and reference members.Preferably, from the standpoint of increasing the indicator andrecording range of the dosimeters, it is desirable to employ two or morephotosensitive recording strips which are formed of photosensitivematerials having different film speeds for nuclear radiation. With suchan arrangement, it is desirable to associate a reference strip with eachphotosensitive recording strip.

Ano-ther common characteristic of the various dosimeter embodimentsresides in the provision of a strip or portion of unexposedphotosensitive material which is sensitive tolight and heat but which isrelatively insensitive to nuclear radiation in doses of a magnitudeequal to the greatest dosage likely to be encountered or to the maximumdosage adapted to be indicated or measured by the dosimeter, e. g., todosages of about 500 roentgens. Such a strip or portion of unexposedphotosensitive material is useful to show, by the density of itstransfer record, the successful operation or the failure of thedosimeter and in this regard affords a guarantee. Attention is herecalled to the fact that the photosensitive materials employed for therecording strips are so much more sensitive to nuclear radiation thanthe photosensitive material used with the guarantee strip or portionthat exposure of the former may be effected without exposure f theguarantee strip or portion.

With regard to failure of the dosimeter, it is pointed out that such mayarise from a variety of causes. Among these may be mentioned the leakageinto the envelope of actinic light whereby to prematurely expose thephotosensitive materials therein or the fogging of such photosensitivematerials by the subjection of the dosimeter to high temperatures, orfor other reasons, such as the failure f the processing liquid, as forexample from oxidation of the developer or by mechanical failure due tothe improper processing of the dosimeter.

In the embodiment of the invention shown in Figs. 1 and 2, thephotosensitive element is illustrated as comprising a support 27 towhich two photosensitive recording strips 29 and 31 are secured, as bymeans of a suitable adhesive. Each photosensitive recording strip 29 and31 comprises a conventional film base 33 on which is supported a silverhalide emulsion. The emulsion or layer of photosensitive materialassociated with the recording strip 29 has a faster film speed withregard to the radiation to be detected than has the emulsion 37associated with the recording strip 31. The photosensitive element 15also includes two photosensitive reference strips 39, each of whichcomprises a conventional film base 43 on which is supported a silverhalide emulsion layer 41. The photosensitive material of each referencestrip 39 has a similar film speed for nuclear radiation and is soinsensitive or slow to nuclear radiation as to remain substantiallyunaffected by the radiation dosages expected to be encountered.

Each of the photosensitive strips 29, 31 and 39 extends longitudinallyof the support 27 and is spaced transversely thereof and in symmetricalrelation. Preferably, the recording strips 29 and 31 will be locatedcentrally of the photosensitive element with the reference strips 39positioned towards the outer edges of the element 15. Rectangularlyshaped spacer strips 45 of paper, cardboard, plastic sheeting, or thelike, extend longitudinally of the photosensitive element 15 adjacenteach long edge thereof in spaced relation to the photosensitive strips39 and are utilized for a purpose which will hereinafter becomeapparent.

By construction, the photosensitive element 1S is only slightly longerthan the print-carrying element 1S. It is therefore preferable to securethe photosensitive element 15 to the layer 11 by a strip e4 ofpressureand/ or heat- '6 sensitive adhesive, rather than by heat-sealingthe photosensitive element to the layer 11, whereby to prevent possiblefogging of the phetosensitive materials which form the element 1S. Thisadhesive strip 44 is engaged by the element 15 across one end thereofand is also engaged by the wall-forming member or layer 11.

With specific regard to the reference strips 39, it is to be noted thatthey have been subjected to preexposure and therefore contain latentimage. This preexposure is made through a scale of gray tones in stepsof increasing optical density which extend lengthwise of each referencestrip from at least adjacent one end thereof towards the other end ofthe strip. In Fig. l, the latent image gray scale steps on eachreference strip 39 are diagrammatically indicated as lying within theareas denoted by the reference character 139. Each latent image grayscale step is formed by an exposure which will produce a transfer printon the print-receiving element 13 having an optical densitysubstantially equivalent to the transfer print produced by exposure of arecording strip 29 or 31 to nuclear radiation of predeterminedintensity.

Each reference strip 39 is shown as having six gray scale steps 139 oflatent image. A greater or lesser number of gray scale steps may beemployed. The steps 139 may be formed to provide transfer prints on theprintcarrying element i3 in the form of steps which vary in opticaldensity from white or near white to black or near black. Each referencestrip 39 may be exposed so as to form similar set of gray scale latentimages therein. lt is, however, within the scope of the invention todifferently expose each reference strip 39 so as to provide dissimilarsets of gray scale latent images. For example, the left and rightreference strips may be exposed so that together they produce gray scalemeans which together provide l2 steps covering a density range of fromwhite or near white to black or near black.

For practical purposes, however, it has been found satisfactory to givesimilar exposures to all reference strips 39 so that each strip willproduce a transfer print of a similar gray scale having six steps whichvary in retiection density over a range of from about 0.2D to aboutl.5D. in Fig. l the latent image of step 139 having the least exposureis located at the bottom end of the photosensitive element 15 while thegray scale step of greatest exposure is located towards the top of thephotosensitive element.

Mention has been made of a guarantee strip or portion on thephotosensitive element. In the event that the bottom gray scale step139, as viewed in Fig. l, is substantially unexposed, this may serve asa guarantee portion. Alternatively, if the gray scale is printed onlyover a part of a reference strip 39, the unexposed portion of thereference strip may be used as the guarantee portion. Such a portion isindicated at 239 on each of the reference strips disclosed in Fig. l.

The print-carl: ng element 1S may comprise a suitable permeable materiaih, for example, as paper or the iike, and is adapted to be secured tothe inner surface of the wall-forming member or layer 12 as byheatsealing to the plastic coa g on the layer, or by means of anadhesive strip positioned transversely of the element and engaged withan end thereof and with a part of thlayer i2, or it may be secured byother appropriate means.

As be noted, indicia, such as the letters A, B, C, and so on to L,extend along each side of the print-carrying element These charactersmay be formed by conventional mechanical printing or other practicesdirectly onto the surface of tr e print-carrying element 1S or they maybe printed or otherwise formed on separate strips which are secured tothe element 18. As shown in Fig. l, there are a series of six characterson each side of the print-carrying element Thus, each character isreferred to a gray scale step f3@ on the photosensitive element 15 andis adapted to provide an indication of the intensity of the radiationrepresented by the transfer print of that particular gray scale step139. Each letter of the indicia l represents intensity of radiation inroentgens. Instead of this practice, the intensity in roentgens may besubstituted for the letters. ln any event, the indicia 188, togetherwith the transfer print of each gray scale, are adapted to provide ameasuring reference with which the transfer print of each recordingstrip formed upon processing the dosimeter may be compared.

The container 2l) is formed of a sheet material such as that employed inproviding the wall members 1l and 12 of the envelope and comprises abase of kraft paper, such as the layer 2l, a layer of aluminum or leadfoil, such as the layer 23, and a coating of a thermoplastic material,such as the coating 25. Rupturable containers of this character may beformed from a rectanguiarly shaped blank which is folded over uponitself and is heat-sealed around its periphery, the container beingfilled with the processing liquid prior to completion of theheat-sealing. Preferably, the container Ztl is provided with a weakerseal along its dispensing mouth portion than along other sealed portionsof the container. One convenient marmer of providing a weaker seal is tocoat a narrow area on one surface of the container blank adjacent themouthforrning edge thereof with a thermoplastic material which has alesser athnity for a thermoplastic material like that of coating thansaid coating has for itself. As one example of a thermoplastic materialof this character, mention is made of ethyl cellulose. Details ofcontainers of the general character suitable for use with this inventionare disclosed in the copending application of Edwin H. Land, Serial No.652,6l2, filed March 7, 1946, for Fluid Containers now Patent No.2,634,886 issued April 14, 1953.

The just-described practice for obtaining a weaker seal is also usefulin connection with the wall members lll and l2 whereby to assist infacilitating and assuring their separation following a processingoperation. Thus, for example, the wall member lll may be striped with amaterial such as ethyl cellulose over a portion 47 thereof locatedadjacent the leader i7. This expedient provides a bond adjacent theleaders le and 17 which will be weaker than the bond along the peripheryof the sealed unit.

Print-carrying element l5 preferably comprises a support on which iscoated a liquid-permeable material, preferably gelatin. Examples ofprint-carrying elements which are especially suitable for this purposecomprise photographic materials known to the art as imbibition paper andbaryta paper. Other materials include waterpermeable plastics such asregenerated cellulose, polyvinyl alcohol and the like. Betaileddescriptions of suitable materials for the print-carrying element aredisclosed in the aforementioned United States Patent No. 2,543,181.

As already noted, the silver halide emulsions 35, 37 and 4l aredifferently sensitive to nuclear radiation and consequently havediiferent lilrn speeds with respect to such radiation. The leastsensitive emulsion is the emulsion 41 employed in the formation of thereference strips 39. A photosensitive material is selected for the slowemulsion 4l which is relatively insensitive to X-rays and gamma rayswhereby latent image resulting from exposure to nuclear radiation willnot be formed unless the radiation is in a quantity of around 1G90roentgens, which exceeds the maximum expected dose. Silver halideprinting papers, especially the so-calied contact papers, are suitablefor this purpose. A contrasty sil er halide contact printing paper ofthis character is commercially available under the name of Velox t3-4.

ln the embodiment shown in Fig. 2, the emulsion 29 has the fastest iilmspeed for nuclear radiation. The layer employs photosensitive materialin which latent image will be formed when the material is subjected tofrom about 5 to l0 roentgens and which will become completely exposedwhen subjected to about 50 roentgens. Conventional silver halide copyingpapers of high contrast and high speed with respect to light waves, andespecially papers employed in projection photocopying, are suitable forthis purpose. A copying paper of this character is commerciallyavailable under the name of Kodagraph Projection Ledger.

The photosensitive material providing the layer 31 is of intermediatespeed as compared to the photosensitive material of layers 4i and 35.The layer 31 employs a photosensitive material in which latent imagewill be formed when the material is subjected to about 75 roentgens andwhich will be completely exposed when subjected to about 500 roentgens.For this purpose, a conventional high speed silver halide enlargingpaper is useful. A specific example is enlarging paper commerciallyavailable under the name of Royal Bromide F-4.

ln using the emulsions just described, it will be apparent that thedosimeter has a range of from 5 to l0 roentgens to about 5G() roentgens.The latter dosage is often fatal, as it is commonly known.

The liquid processing composition employed in container Ztl for use withsilver halide photosensitive material comprises an aqueous alkalinesolution of a photographic developer and a silver halide solvent towhich a thickening agent, such as sodium carboxymethyl cellulose, hasbeen added. Detailed examples of suitable processing compositions arecontained in the aforementioned United States Patent No. 2,543,1831.

in processing the sealed dosimeter itl, the leader portions ll6 and i7are inserted between suitable pressureapplying members, which will bedescribed in more detail hereinafter, and the unit as a whole is movedtherebetween by manually grasping the leaders and pulling the dosimeterentirely through the pressure-applying members which are held inrelatively fixed position. As a result, the container 2i) is rupturedand the liquid content thereof is discharged and spread between theoverlying faces of the emulsion layers 35, 37 and 4l and the face of theprint-carrying element l.

The spacer strips 45 on the photosensitive element 15 are adapted tocontact the print-carrying element 18 adjacent the sides thereof and tocover the indicia 183 when the layers i1 and 12 of the envelope arepressed together during processing and assist in controlling thespreading of the processing composition and in conning the liquidthereof to an area of the print-carrying element lying within theconfines of the spacers. While spacer strips are, in general, desirablefor the purposes just outlined, it is possible to obtain excellentprocessing without their use and their omission from the dosimeter unitsdisclosed herein is deemed within the scope of the invention.

With further reference to Fig. 4, it is to be noted that the ends of thephotosensitive and the print-carrying elements which are furthestremoved from the container are spaced from the sealed ends of the wallmembers ll and l2 to which they are next adjacent. The space between theends of the photosensitive and print-carrying elements provided by thisexpedient serves for receiving liquid processing composition in excessof that spread over the superposed faces of the print-carrying andphotosensitive elements. Alternatively, a special trap member or membersbetween which or within which this excess liquid is collected may beprovided within the dosimeter envelope and may be mounted on the innersurface of one of the wall members of the envelope adjacent the end ofthe photosensitive or the print-carrying element, or trap means may beprovided by a special construction for the photosensitive andprint-carrying elements, for example the construction illustrated in thedosimeter of Fig. 6.

After rupture of the container and spreading of its contents, thedosimeter is kept in sealed condition for about a minute to completetransfer processing. The Wall members il and 12 are then stripped orseparated from u each other by grasping a leader portion lo and i7' byeach hand and peeling the dosimeter apart.

As a result of processing, a transfer print of the latent image grayscale on each reference strip 39 is formed on the print-carrying element18 adjacent each set oi indicia lt'ib. In accordance with transferprinciples, the print the most exposed gray scale step on aphotosensitive strip 39 will have the least density of the gray scalesteps formed on the print-carrying element. rhis is because each grayscale step which is printed by transfer on the print-carrying element isa reverse image or" the corresponding gray scale step photographicallyprinted on the photosensitive element l5.

Thus, the least exposed area on each reference strip 39 Will have thedensest transfer print, while the most exposed area on each referencestrip 39 will have the least dense transfer print. Consequently, thestep A of the indicia A to F will appear as the darkest or inf-st densestep for that set of indicia, while the step F will appear as the stepof least density. A similar situation exists in connection with thesteps G and L of the indicia set G to L. Under these circumstances, themeasure of radiation dosage increases with decrease in density of thetransfer prints oi the gray scale steps. Hence, steps A and G will showthe least dosage for their respective indicia sets, while steps F and Lwill show the greatest dosage.

Processing of the unit will provide prints of the recording strips 29and 3i centrally or" the print-car fing element i8 and extending fromend to end thereof. The density of these prints is matched against agray scaie step opposite a set of indicia A to F and G to L. Assumingthat neither of the photosensitive recording strips and 3l have beenexposed by nuclear radiation, the transfer prints forrned of eachrecording strip will have a high density which is equivalent to the highdensity of step A and of step G of the respective scales.

On the other hand, if either of the photosensitive recording strips 29and 3l has been subjected to nuclear radiation, the density of thetransfer print formed thereby will be found to match lsortie gray scalestep other than the step A or G. inasmuch as the user of the device willknow what each gray scale step represents in terms of radiation dosage,he is able to determine the dosage to which he has been subjected bycomparing the transfer print of a recording strip with the appropriateindicium lS.

It is important to keep in mind that the photosensitive recording strips29 and 3l. have different lrn speeds. Thus, it is possible to completelyexpose the strip of faster lilrn speed without exposing the recordingstrip 3i. ln this event, the transfer print of the recording strip 29will have a low density at least equal to the least dense step on thegray scale opposite the indicia A to F, While the transfer print of therecording strip Si will have a high density equal to or greater than thedensity of the step G ofthe indicia G to L. On the other hand, if theradiation is of an intensity suiiicient to expose the recording strip3l, it is to beobserved that the record ing strip 29 will also becompletely exposed.

A transfer print of guarantee portion 239 of each reference strip 39should record the highest density when the dosimeter has satisfactorilyoperated. information is at once conveyed that the dosimeter has failedfor one of the previously mentioned reasons or for other causes if thistranfer print is less than the high density just described. Under thelatter circumstances, any reading obtained by the dosimeter isvalueless.

Various modifications in construction of the dosiineter unit fall Withinthe scope of the invention. For example, in Fig. 5 a dosimeter unit Stiis disclosed wherein the overlying wall members of the envelope are eacha part of a continuous strip of appropriate sheet material which isadapted to be folded along its transverse axis at the diagrammaticallyindicated fold line -tl whereby .a tti to form layers Eli and 5l?. whichare adapted to overlie each other and to be sealed together in themanner described i4 connection with yers 1l and l2 of the doeter Thesheet ma ia?. which provides the eniorniing :nein ,.s for the dosirneter:itl ally similar to the material used for .he layers Also, the freeends of wall-forming layers d are provided with suitable leader portions(not shown).

@ther structural variations are illustrated in Fig. 5. In

the iniage-carrying element S13, and not the u-crsitive element as inFig. l, has spacer strips 54S :lo nted adjacent the longitudinal edgesthereof. This istruction perniits indicia 588 such as the indicia sets Ato l: and to L to be printed on the upper surface of sp -er strip.Alternatively, a single piece of sheet may employed for theprint-carrying element. 'istat-ice, the grey scale indicia will beprinted long the edges of the print-carrying element, and spacer stri sof transparent material, which are mounted over the printed indicia,will be employed. Otherwise, the print-carrying element f issubstantially similar to the printca1rying element ll?) heretoforedescribed and, like the element it, is secured to the inner surface ofthe layer by heat-sealing.

By way of further inodiiication, the dosinieter i use of a photos ritive element 5?'.5 which comprises a U-shaped member of photosenitivereference nia terial and photosensitive recording strips and 5331 whichare loc between arms of the U-shaped inerti-ber. rihe t5-shaped maniocand the photosentitivc recording strl fo each comprise conventional nlmwhich carries a photosensitive r-.ra erial of the c vr heretofore dscribed. ln this regard, the photose Ie materials for the irl-shapedineniber a d the recording strips and 53E correspond respectLely to thephotosensitif-e materials dctailed in connection with the strips 29, 3l.and A suitable strii adhesive tape or other materil is engaged with theinner surface ot the wall-fo g layer S i and with the 'rj-shapedreference member adjacent the ends of the arrns thereof and with eachrecording strip S29 and if for securing the photosensitive element tothe layer The photosensitive element CES is positioned on thewah-forming layer for registration with print-carrying element when thelayers Sill and Si?, are folded overupon themselves. Under theconditions described, the base ot tue U'shaoed met rber will be alignedwith an end of pri car ing element ti/hen jne unit is in spree-dontcondition shown in Fig. 5.

A container sir to the contain to be mounted at the end of the printwhich is most distant from the photoseicA l' when the envelope Wall-foing members are in si eadapart condition. Except fol the aboveaiotedditeiences, the dosimeter is lilac the dosirneter in `Figs. l through 4.

it is to be understood that the photosensitive reference member 5339 isadapted to have undeveloped or latent image gray scale formed to extendalong each thereof at a location adjacent the photosensitive recordingstrips and by photographic printing practices. lier the purpose ofsimplifying the drawings, no attempt has been triade to illustrate thesegray scales, which are similar to the latent image gray scales of r'lnasmuch as the U-shaped reference member made entirely ofphotosensitive material, a guarantee portion will be provided by thebase of the tJ, which portion of the member S39 will be completelyunexposed.

Operation and processing of the dosimeter 5@ is generally similar in allrespects to the operation and processing of the dosiineter it?.

A preferred embodiment oi the invention is disclosed in Fig. 6, whereinthere is illustrated a dosinieter which it, is pted element ele. .ent

il is generally indicated by the reference numeral 6b and which isgenerally similar to the dosimeters lil and Sil in that it makes use ofindividual and sealed-together envelope-forming layers or wall-formingmem ers 6M and 612 having leaders 616 and 6l7 and a container 621i whichemploy materials and constructions substantially identical with thecorresponding wall members and containers of the dosimeters lll and Sil.The differences between the dosimeter 66 and the dosimeters l@ and Silreside in the constructions employed for the photosensitive andprint-carrying elements thereof.

Unlike the dosimeters l@ and Sil, the dosimeter 6@ ernploys a preformedgray scale which is mounted on the print-carrying element. By apreformed gray scale we mean a gray scale having the density stepsthereof in a visible condition as distinguished from a condi t wherethey are potentially visible and dependent upon processing of thedosimeter to render them visible, es in the case of a latent image grayscale such as that previously described. Preformed gray scale beprovided by mechanical printing practices or by appropriatephotoexposure and development o photosensitive material or by acombination of these ln fact, it has been found that a combinatongraphic printing and development and mechanical priA ing is well adaptedfor forming the gray scale means ernployed with the dosimeter 66. rhus,the gray scale may be photographically printed on a portion or" a stripof a silver halide emulsion and the strip then developed to provide thegray scale, after which the indicia associated with the gray scale stepsare mechanically printed on an unexposed and fixed portion of the strip.rl'he practice which makes use of a preformed gray scale is advantageousin that it avoids the possible occu r -ce change in latent image whichremains undeveloped for long periods of time.

With particular reference to Fig. 6, the print-carrying clement 61rd isformed of a rectangular sheet of imagereceptive material, for examplebaryta paper, and is secured to the wall member 612 by 'neat-Sealife. lnthis embodiment of the invention, the gray scale are individual members639 which are adapted to be mounted on the envelope wall 6332 onopposite sides of the printcarrying element 618 and between theprint-carrying element and the long edges o the dosimeter and to besecured thereto by heat-sealing. Each gray scale member 639 is providedadiacent one edge thereof with the usual longitudinally extending rowsix density steps and also with a row of lettered indicia 633 locatedalong the other long edge of the member. Each member 639 is positionedso that the gray scale thereof is located next to the print-carryingelement 61S.

in Fig. 6, the gray scale and indicia formed on the member 639 arerespectively provided by photographic and mechanical printing practicesas heretofore described and, in this regard, the material used tor thegray scale members 639 comprises an appropriately exposed, developed andixed silver halide emulsion layer carried on a conventional hlm base.The members 69d, in addition to ing gray scale mi "s, are also intendedto function as spacers by utiliz g, as shown in Fig. 7, a material forthe gray scale members which is thicker than the material providing ther 'nt-carrying element did. if the emulsion laer and ii i base etnploycdtor forming the gray scale member do not possess the desired thiol-mess,one or more ig strips of suitable paper, for example .kraft paper, maybe adhered to bottom or outer surface olthe hlm base. in this reg rd, itis to bc noted that each gray scale nicmare intended to Thephotosensitive element 615 of the unit 6i) employs a plurality ofrectangularly shaped photosensitve strips, each of which comprises asilver halide emulsion layer upported on a conventional lm base. Threesuch photosensitive strips are disclosed, namely, two photosensitiverecording strips 629 and 631 and a photosensitive strip 649 in the formof a guarantee strip. All photosensitive strips are unexposed prior touse. The recording strips 62 and 63l malte use of photosensitivematerials similar to those described in connection with the strips 29and 3l. Thus, the strip 629 will have the highest lm speed to nuclearradiation of the photosensitive strips disclosed in conjunction with theelement 615, while the recording strip '631 will have the next highestiilrn speed. The so-called guarantee strip 649 is an emulsion comparablewith that described in connection with the reference strips 39 of Fig. 2and consequently is very insensitive to the radiation to be detected.

In the embodiment of the invention disclosed in Fig. 6, the recordingstrips are relatively wide and each recording strip is located adjacenta longitudinal edge or a long side of the photosensitive element. As maybe noted, the photosensitive recording strips 629 and 631 are spacedapart whereby to permit the guarantee strip 649 to be located betwenthem and centrally of the photosensitive element 6l5. Recording strips629 and 631 are made relatively wide so as to provide a photosensitiveelement having a width which is substantially similar to the width ofthe print-carrying element and its associated gray scale 639. In fact,it may be said that preferably the photosensitive and print-carryingelements in all embodiments of the invention should possess similarwidths.

The members which make up the photosensitive element 615 are eachconsiderably longer than the printcarrying element 61S. Consequently,the photosensitive strips 629, 631 and 649 may be heat-sealed to theinner surface of the wall member 611 at their ends which are located thenearest to the leader 617 without fear of ogging those portions of thephotosensitive strips adapted to overlie and cooperate with theprint-carrying element 618 whereby to facilitate assembly of the unit.Alternatively, the photosensitive strips which provide thephotosensitive element 615 may be secured to the envelope wall member bymeans of an adhesive strip, such as the strip 44 of Fig. 1, or thephotosensitive strips may be mounted upon a support layer, such as thelayer 27 of Fig. 2, and this support layer may be either heat-sealed tothe wall member or secured thereto by an adhesive strip. As may benoted, a corner of each strip 629, 631 and 649 is cut away. Thisexpedient is employed to facilitate assembly, especially when carriedout in a dark room, by assisting in correctly positioning thephotosensitive strips.

It is also to be observed that the two photosensitive recording strips629 and 631 are respectively provided with extension portions 650 whichoverlie and which are adapted to cooperate with the extensions 640 onthe gray scale members 639 during processing to provide trap means forreceiving and trapping excess processing liquid following the rupture ofthe container 620 andthe spreading of its liquid content within thedosimeter envelope.

Use and processing of the dosimeter 60 is substantially similar to theuse and processing of the dosimeters heretofore described. With thedosimeter 60, however, the transfer print formed by the guarantee strip649 will appear centrally of the print-carrying element 618 and willextend from end to end thereof.

While the dosimeters illustrated in Figs. l through 8 have been shown asindividual, unconnected units, it will be appreciated that a pluralityof such dosimeters may be secured together in end-to-eud relation toprovide a fanfold type of unit. For example, the end of the leaders of asealed dosimeter may be suitably secured to the sealed end of anotherdosimeter, as by the use of an adhesive and heat-sealing or by the useof an adhesive strip, and so on, to provide a strip ofconnected-together dosimeter envelopes which may then be fanfolded.Alternatively, any of the dosimeters shown in Figs. l through 8 may besecured to a surface of a suitable baci;- ing or support sheet atappropriate intervals for fanfolding.

This last-mentioned arrangement is illustrated in Figs. 9 and l0 whereinthe fanfold type of unit comprises a continuous backing sheet lll@ onwhich individual and similar dosimeter envelopes l1() are mounted andsecured by a strip 7.2@ of a pressureand/ or heat-sensitive material atappropriate intervals to obtain the fanfold as shown in Fig. l0. in thisregard, adjacent dosiineter envelopes are separated by spacing intervalsat least equal to the length of an envelope. The backing or supportsheet lil@ is made sufliciently long to provide a leader portion i3d anda trailer portion 14@ thereon.

The dosimeter envelopes l1() are diagrammatically shown and are intendedto represent any of the dosirneters heretofore described in detail.Leader portions for the envelopes lll@ may be omitted or are preferablymade considerably shorter than the leaders 16 and 17 or 6l6 and dlp'. ifdesired, the backing sheet may be coated with an appropriatepressureand/or heat-sensitive adhesive for securing the dosimeters il()thereto and such practice may be used in conjunction with the adhesivestrips lill or may be employed as the sole means for securing thedosimeters to the backing sheet 100.

The dosimeters described herein are intended to be carried on the personand to be processed at the instant that the possessor of the devicewishes to determine if he has been subjected to unsafe radiationconditions. Consequently, the dosimeters are relatively small. Forexample, the complete envelope in any of the embodiments heretoforedisclosed may have dimensions of about three inches by one inch or evensmaller.

Under the just noted-circumstances wherein the dosimeter is literallyintended to be processed at an instants notice, it is desirable toprovide processing means of simple and light-weight construction forassociation with the dosimeter. Preferably, the processing device shouldbe of a size and weight such that it may be carried on the person, as byattachment to an article of clothing or by suspension around the neckfrom a ribbon or cord, as in the case of the so-called military dog tag,or even carried in a pocket. Also, the processing device shouldpreferably be in the nature of a holder or carrier for storing orholding one or more dosimeters while protecting them from dirt, moistureand the application of forces which would rupture the liquid containersof the stored dosimeters. At the same time the processing device shouldbe able to maintain the stored dosimeters in a generally flat conditionready for use and also should shield them from soft rays which mightprematurely expose their photosensitive materials.

One embodiment of a processing unit, possessing the justanotedcharacteristics, is generally indicated by the reference character 7d inFigs. ll and l2 and makes use of top and bottom cover members 71 and 72,respectively. Each cover member 71 and 72 comprises an elongated base inthe form of a plate having bent-up portions which provide wall means.The upper cover member 7l is slightly wider than the lower cover memberso that it may be engaged with the lower cover member to partiallyencase the latter. In the embodiment of the invention disclosed in Figs.ll and 12, the cover members '7l and 72, when engaged with each other,are adapted to provide a boXlike structure in the nature of a container,as will become fully apparent.

in the case of the top cover member 71, side walls 'i3 and end wallmembers '75 and 77 are provided, while the bottom cover member 72 onlyhas side Wall members 74. As may be noted, the end Wall member 75 isprovided with an opening 79 therein and has its end most distant fromthe top plate bent over upon itself so that it is generally parallel tothe top plate. The bottom cover member 72 has an elongated tongue 76which extends from one end of the body of its base plate. Tongue 76 isadapted to be inserted within the opening 79 and is provided at itsedges with ears 81 which are capable of being bent up so as to securethe cover members together. A suitable opening for engagement with asuspension cord or the like is shown as formed in the tongue 76.

v"il be c Ifpreciated that the mounted cover means l. wil. connectedtogether at one end by con-u nect.' g means which permit them to bemoved into and out of sbperpesed and generally parallel relation withrespect to each other. Fig. il shows the cover members relation and itis to be observed that the n provided by the tonga-e 76, ears iii andend fn' ions in the general nature of a pivot whereccver members may bespread apart in angular 'with respect to each other for loading theholder .ovino a dosimeter therefrom. it is to be noted the bon-nire sctnrc provided by 1the superposed coser members 7i and 72 is open at theend thereof which is removed from the end having the pivotal con- 25 onfor the cover members whereby' to permit withf'ai of a dosi aeter fromthe device when undergoing eans for securing the cover` members inclosed relabail member which is piv'c-taily secured 30 to the papersurface of the base plate of cover member ion is late of the bottom tt.e cover members =diticn aga st forces tendo spread their; apart when ebail is in the ed posi on shown in Vfig. l2. sprain. aait, rnptiiringthe container in "daer spreading the contents thereof `vithin "e..envelope, is incl 1 le-' within the device '7%. t...s spreader comprisestwo spreader memtich wili be heid in Contact with each other whenrnen'ibers are closed and bett/veen which the moved to carry ont aprocessing operation. e such spreader is icatcd at 52. as con ad rodmember y ich extends from side E d is tixediy all or the bottom cover 72isvcrsely thereof location for Contact reader member. The other spreadermember is d at an end portion of a iiat f which nas its opposite endfixed to the end of c plate of cover member 7l adjacent the end wallSnr-ing Se is so constructed that when described and shown, it is conomthe top cover me :aber il and t' e Aareader .ieinber S2. The spreaderthe spring Sli is a bent portion thereof which is suitably rounded andis located for contact with the sr der member As may be observed, spring65 Se, at over the S55, has a width subl`| -iy equal to the interiorwidth .d Fihese spreader members are s"bstantiallyY L araliel to eachother and effectivfly close the of the processing holder when the insnperposed parallel relation whereby to assist in retaining a dosimeterwithin the device.

use of the processing device 7i), a dosinieter envelope should always belocated between the spring S4 the inner surface of the low r covermember 72. Means are provided in the processing device to prevent `15improper loading 'of a dosimeter. These means make aise of the retainerplate 91 and shape this plate to extend aaround the end wall v77 of thecover .plate 7l to provide ra projecting 'lip portion 97 whichlprotrudes into the :interior of the processing device. The lip portion97 is sufficiently long to engage an y'extension 94 formed on the freeend of the spring spreader member 85 whereby .the movement of the freeend of the spring 84 is restrained. Regardless of the width of therestraining lip 97, it will be appreciated that this construction makesit substantially impossible to insert a dosimeter between the :spring 84and the in'ner surface of the upper cover member 71. However, movementof the spring 84 is always isuicient to bring the spreader member 85thereof -into 'proper processing contact with the 'spreader member S2.

For storage purposes, 'a dosimeter is adapted lto have the leader or tabportions thereof folded over one outer 'face of the dosimeter envelope,as shown in Fig. 4. The processing "holder 7l?, as in the case of allprocessing devices disclosed herein, has a length sufficient to carry fadosimeter folded for storage so that thc dosimeter is positioned betweenfthe connected ends of the holder and the spreader members 32 and 85 andis free of engagement with the spreader members. This is advantageous:since it protects the leader portions of the stored dosimeter fromdamage. Preferably, the interior 'of the processing device is largeenough to carry two or more dosimfeters in the storage condition 4justdescribed, with one dosimeter superposed upon another.

It is 'desirable to provide the processing device with shield means tocounteract the excessive effect of soft rays, as for example X-rays oflong wavelength which have a low penetrating power, onthe photosenstiveportions of a dosimeter stored within the holder. These shield meanscomprise a liner of a material tending to attenuate such radiation by anappropriate factor and may comprise lead or cadmium or other heavy metalor alloy.

ln Figs. ll 'and l2 shield members S7 and are shown as carried,respectively, by the inner surfaces of the base plates of the top covermember 7l and the bottom cover member 72;. Shield members 87 and 88 maybe fixed to the cover members by any suitable means, such as by rivetsor by the use of suitable cements and/ or adhesives. lt is also possibleto mount either or both of the shields 57 and 88 upon the exterior ofthe cover members. lt is to be noted that the spring member dal isU-shaped and that shield member S7 is located between the arms of thespring as a construction expedient to conserve space.

it is to be noted that the shields S7 and S3 are of a generallyrectangular shape and have their longitudinal axes centered on thelongitudinal axis of the container', The shield members are of a widthsulhcient to cover the photosensitive emulsions of the photosensitiveelement of a dosimeter mounted within the holder and are so positionedthat these photosensitive portions will be fully covered when adosimeter is placed in the holder device for storage. Shields 37 and S8provide predetermined attenuation of soft rays incident thereon wherebyto counteract their effect upon the photosensitive materials within thedosimeter envelope. ln cases where soft rays are encountered which areat other than normal incidence, as for example rays which make a largeangle with the shield members 37 and S8, it may be desirable to provideadditional shield members along the side walls of the processing device.

Operation of the processing device 70 will be apparent from theforegoing. rflue manner in which one or more dosinieters may be loadedinto the device for storage has already been described. Assuming that adosimeter is stored within the device and it is desired to process thedosimeter, the bail member 93 is moved to its un/ latching position andthe cover members 71 and 72 are spread apart about their connected endsas a pivot whereby to permit the stored dosimeter to be removedtherefrom. The folded leader portions of the dosimeter are id thenstraightened so that they are portion of the envelope and the dosimeteris inserted between the open cover members this condition and with theleader portions thereof located between the spreader members 82 and 85.Following this, the cover members are moved into their closed orsuper-posed position and are secured by the bail member 93. Theprocessing device 70 is then held in one hand and the protruding leaderportions are grasped with the fingers of the other hand and are pulled,whereby the dosimeter is pulled between the spring-loaded spreadermembers d2 and 85 and entirely out of the processing unit 7d.

It is to be noted that the spreader members S2 and 85 are inspring-loaded contact with each other when the cover members of theprocessing device 70 are in closed position and no dosimeter is engagedbetween the spreader members. Gn the other hand, the spreader memberswill be separated to some extent when the cover members of theprocessing device are closed and when a dosimeter is engaged between thespreader members. The spreader members 32 and 8S, in effect, providemeans for applying pressure to the opposite sides of a dosimeter whichis `engaged between the spreader members and which is pulled betweenthem whereby to effect the rupture of the container and the spreading ofits liquid content.

Spring ed is designed to create a pressure or force which is surlicientto rupture the container of a dosimeter undergoing processing and whichis great enough to spread the liquid content of the container in a thinlayer within the envelope of the dosimeter. Consequently, during thespreading operation itself, the separation between the spreader members$2 and d5 will remain substantially equal to the thickness of the bodyportion or" the dosimeter, i. e., the thickness of the wall members ofthe envelope plus the thickness of the print-carrying eiement and thethickness of the photosensitive element, including spacer means withinthe dosimeter element.

Processing device 7G, as well as all of the embodiments thereofdescribed herein, may be formed of any suitable material such as metalor organic plastics. Even wood may be used as a construction material.Whatever material is employed, a material having a lioht unit weight ishighly desirable. Of the metals, aluminum is a preferred material. Otherlight-weight metals and alloys may of course be used.

A processing apparatus, similar to apparatus 7@ of Figs. 11 and l2, mayalso be used for holding and processing the fanfold unit of Figs. 9 andit). ln this connection, the processing apparatus will be made sucientlydeep to receive the plurality of dosimeters of the fanfold unit and willsuitably locate the spreader members of the apparatus so that theirspreading surfaces will be appropriately aligned for receiving theleader end of the fanfold pack. Processing of the fanfold pack will beapparent from the foregoing. After loading a fanfold pack into aprocessing apparatus, the leader portion 13d of the pack will extendfrom the apparatus and the first dosimeter of the pack may be processedby exerting a pulling force on the leader to draw the lirst dosimeterenvelope through the spreader members.

in processing the first dosimeter, the fanfold pack is withdrawn fromthe apparatus so that at least a portion of the pack which forms thespacing interval between the first and second dosimeters will extendbeyond the apparatus and so that the second dosimeter of the pack ismoved into ready position for processing by the spreader members of theapparatus. The processed dosimeter is disconnected from the unit bycutting or tearing the portion of the fanfotd pack which forms thespacing interval between the "nrst and second dosimeters at a positionadjacent the trailing end of the processed dosimeter. Processing of thesecond remaining dosimeters of the fanfold pack is vcarried out in amanner similar to that just described.

While the invention has been described in connection with spec?Photoseusitive materials which provide an aligned with the bodyeffective 'range for the dosimeter of from about 5 to 500 `roentgens, itwill be appreciated that other photosensitive materials possessingdierent ranges of sensitivity may be substituted for those shown by wayof illustration. Such a variation is deemed within the scope of theinvention.

From the foregoing it will be appreciated that the aims and objects ofthis invention have been accomplished in the provision of a variety ofdosimeter embodiments, all of which are capable of detecting,indicating, recording and measuring radiation dosages and which may bequickly processed on an instants notice.

Since certain changes may be made in the above products withoutdeparting from the scope of the invention herein involved, it isintended that all matter contained in the above description or shown inthe accompanying drawings shall be interpreted as illustrative and notin a limiting sense.

What is claimed is:

l. In a unit which contains photosensitive material for detecting andindicating the presence of nuclear radiation, in combination, anenvelope having a pair of Wall members which are each substantiallyimpervious to processing liquid employed with the unit and which arearranged in superposed relation with respect to each other, said wallmembers also being further characterized by the fact that they are eachsubstantially opaque to radiation of a wavelength within the visiblespectrum and that they transmit shorter wavelength radiation includingX-rays and gamma rays, a photosensitive element and a printcarryingvelement positioned within said envelope in superposed relation to eachother, a rupturable container holding a liquid processing compositioncarried Within said envelope and in a position so as to be capable ofbeing ruptured and, upon rupture, of releasing its liquid contentbetween said superposed photosensitive and printcarrying elements, saidphotosensitive element having at least one recording strip ofphotosensitive material comprising a heavy metal salt which, uponphotoexposure to nuclear radiation to be detected, as well as to visibleradiation, is capable of having formed therein latent image which isdevclopable to the metal of said salt, said print-carrying elementcomprising a sheet material for supporting print-forming componentstransferred from said photosensitive element upon development andprocessing of latent image, said rupturable container holding as aprocessing liquid at least a thickening agent and a solvent forphotographic processing material, said envelope having positionedtherein photographic processing material including at least a developerfor said heavy metal salt, said material being rendered effective uponrelease ot' said liquid and being in sucient quantity to process latentimage in said photosensitive element and to provide a positive print bytransfer on said imagecarrying element, and a reference strip carriedwithin said envelope and having means capable of providing a scale ofgray tones extending in steps of increasing optical density fromadjacent one end of said reference strip towards the other end of saidreference strip and against which the optical density of the transferprint can be compared, said reference strip and said means thereof whichare capable of providing a scale of gray tones being characterized byremaining substantially unaffected in the presence of radiation to bedetected and indicated.

2. In a photosensitive unit as defined in claim l, a reference stripwhich comprises a preexposed photosensitive strip having saidphotosensitive heavy metal salt as the photosensitive material thereof,said preexposed reference strip containing latent image which is formedby the photoexposure of said reference strip through a scale of graytones provided by steps of increasing optical density, said preexposedreference strip comprising a part of said photosensitive element and allsaid strips of photosensitive character, including said reference strip'18 and said recording strip, being arranged in side-by-side relation.

3. A photosensitive unit as defined in claim 1, wherein said referencestrip is provided with a preformed scale of gray tones extending insteps of increasing optical density from adjacent one end of saidreference strip towards the other end of said reference strip andwherein said reference strip and said print-carrying element arearranged in side-by-side relation.

4. A photosensitive unit as defined in claim 1, wherein saidphotosensitive element comprises at least two recording strips of saidphotosensitive material and wherein each recording strip has a differentlm speed.

5. ln a photosensitive unit as defined in claim l, means capable ofproviding an indication of the failure of said unit for carrying out itsdetecting function and comprising an unexposed photosensitive portionwhich is associated with said photosensitive element and which is formedof a photosensitive heavy metal salt possessing a lm speed which isextremely slow to the nuclear radiation to be measured.

6. ln a unit which contains photosensitive material for detecting andindicating the presence of nuclear radiation, in combination, anenvelope having a pair of wall members which are each substantiallyimpervious to processing liquid employed with the unit and which arearranged in superposed relation with respect to each other, said wallmembers being further characterized by the fact that they are eachsubstantially opaque to radiation of a wavelength within the visiblespectrum and that they transmit shorter wavelength radiation includingX-rays and gamma rays, a photosensitive element and a print-carryingelement positioned within said envelope in superposed relation to eachother, and a rupturable container holding a liquid processingcomposition carried within said envelope and in a position so as to becapable of being ruptured and, upon rupture, of releasing its liquidcontent between said superposed photosensitive and print-carryingelements, said photosensitive element comprising at least twophotosensitive strips of silver halide arranged in side-by-siderelation, one of said strips providing a photosensitive recording stripcapable of having latent image formed therein upon exposure thereof tonuclear radiation to be detected, said other strip providing apreexposed photosensitive reference strip which has beenphotographically printed substantially from end to end thereof through ascale of gray tones arranged in steps of increasing optical densitywhereby said reference strip contains latent image, said printcarryingelement comprising a sheet material for supporting print-formingcomponents transferred from said photosensitive element upon developmentand processing of latent image in said recording and reference strips,said rupturable container holding as a processing liquid at least athickening agent and a solvent for photographic processing material,said envelope having positioned therein photographic processing materialincluding a silver halide developer and a silver halide iixer, bothrendered effective upon release of said liquid and in sufficientquantity to process latent image in said photosensitive element and toprovide on said image-carrying element by transfer a reverse print oflatent image developed in said reference strip and in said recordingstrip.

7. A photosensitive unit as defined in claim 6 and having a plurality ofphotosensitive recording strips each of which has a diiferent filmspeed.

8. A photosensitive unit as dened in claim 6 and having a plurality ofphotosensitive recording strips and a plurality of photosensitivereference strips, an individual reference strip being associated witheach recording strip, each recording strip having a iilrn speed which isdiiferent from that of any of the other photosensitive strips and whichis faster than the lm speed of any reference strip, all of saidreference strips having substantially the same film speed.

19 9. A photosensitivel unit as defined in claim, wherein said unitincludes means which are capable of providing Aan indication of thefailure of said unit for carrying out its detecting function and whichcomprise an uneXposed silver halide portion of said photosensitiveelement, said unexposed portion providing said indicating means having aconsiderably slower lm speed with regard to the nuclear radiation to bedetected than that of the photosensitive silver halide of said recordingstrip.

10. In a photosensitive unit for detecting and indicating the presenceof nuclear radiation, in combination, an envelope having a pair of wallmembers which are each substantially impervious to processing liquidemployed with the unit and which are arranged in superposed relationwith respect to each other, said wall members being furthercharacterized by the fact that they are each substantially opaque toradiation of a wavelength within the visible spectrum and that theytransmit shorter wavelength radiation including X-rays and gamma rays, aphotosensitive element and a print-carrying element positioned withinsaid envelope in superposed relation to each other, and a rupturablecontainer holding a liquid processing composition carried within saidenvelope and in a position so as to be capable of being ruptured and,upon rupture, of releasing its liquid content between said superposedphotosensitive and print-carrying elements, Vsaid photosensitive elementcomprising at least one photosensitive strip of silver halide adapted toprovide a photosensitive recording strip capable of having latent imageformed therein upon exposure thereof to nuclear radiation to bedetected, said print-carrying element comprising a sheet material forsupporting print-forming components which are developable to silver andwhich are adapted to be transferred from said photosensitive elementupon processing of latent image in said recording strip, a referencestrip carried within said envelope in side-by-side relation to saidprint-carrying element, said reference strip being provided with apreformed scale of gray tones which extend in steps of increasingoptical 'density from adjacent one end of said reference strip towardsthe other end of said reference vstrip and against which there can becompared the optical density of a transferprint of said recording stripand said reference strip and the preformed gray scale thereof beingcharacterized by remaining substantially unaifected in the presence ofradiation to be detected and indicated, said rupturable containerholding as a processing liquid at least a thickening agent and a solventfor photographic processing material, said envelope having positionedtherein photographic processing material, including a silver halidedeveloper and a silver halide Xer, both rendered effective upon releaseof said liquid and in suiicient quantity to process latent image in saidphotosensitive element and to provide on said image-carrying element bytransfer a reverse print of latent image developedV in said recordingstrip.

ll. A photosensitive unit as defined in claim 10 and having a pluralityof photosensitive recording strips and an individual reference stripassociated with each recording strip.

l2. A photosensitive unit as defined in claim l0, wherein said unitincludes means which are capable of providing an indication of thefailure of said unit for carrying out its detecting function and whichcomprise an unexposed silver halide portion of said photosensitiveelement, said unexposed silver halide portion having7 a considerablyslower film speed with regard to the nuclear radiation to be detectedthan that of the photosensitive silver halide of said recording strip.

References Cited in thele of this patent UNITED STATES PATENTS 2,258,593Black Oct. 14, 1941 2,483,991l Wollan et al Oct. 4, 1949 I 2,496,218Kieer .1am-31, 1950 2,500,422 Land Mar. 14, l1950 2,565,378 Land Aug.21, 1951 2,624,011 Stern DCC. 30, 1952 2,659,825 Land NGV. 17, 1953

1. IN A UNIT WHICH CONTAINS PHOTOSENSITIVE MATERIAL FOR DETECTING ANDINDICATING THE PRESENCE OF NUCLEAR RADIATION, IN COMBINATION, ANENVELOPE HAVING A PAIR OF WALL MEMBERS WHICH ARE EACH SUBSTANTIALLYIMPERVIOUS TO PROCESSING LIQUID EMPLOYED WITH THE UNIT AND WHICH AREARRANGED IN SUPERPOSED RELATION WITH RESPECT TO EACH OTHER, SAID WALLMEMBERS ALSO BEING FURTHER CHARACTERIZED BY THE FACT THAT THEY ARE EACHSUBSTANTIALLY OPAQUE TO RADIATION OF A WAVELENGTH WITHIN THE VISIBLESPECTRUM AND THAT THEY TRANSMIT SHORTER WAVELENGTH RADIATION INCLUDINGX-RAYS AND GAMMA RAYS, A PHOTOSENSITIVE ELEMENT AND A PRINTCARRYINGELEMENT POSITIONED WITHIN SAID ENVELOPE IN SUPERPOSED RELATION TO EACHOTHER, A RUPTURABLE CONTAINER HOLDING A LIQUID PROCESSING COMPOSITIONCARRIED WITHIN SAID ENVELOPE AND IN A POSITION SO AS TO BE CAPABLE OFBEING RUPTURED AND, UPON RUPTURE, OF RELEASING ITS LIQUID CONTENTBETWEEN SAID SUPERPOSED PHOTOSENSITIVE AND PRINTCARRYING ELEMENTS. SAIDPHOTOSENSITIVE ELEMENT HAVING AT LAST ONE RECORDING STRIP OFPHOTOSENSITIVE MATERIAL COMPRISING A HEAVY METAL SALT WHICH, UPONPHOTOEXPOSURE TO NUCLEAR RADIATION TO BE DETECTED, AS WELL AS TO VISIBLERADIATION, IS CAPABLE OF HAVING FORMED THEREIN LATENT IMAGE WHICH ISDEVELOPABLE TO THE METAL OF SAID SALT, SAID PRINT-CARRYING ELEMENTCOMPRISING A SHEET MATERIAL FOR SUPPORTING PRINT-FORMING COMPONENTSTRANSFERRED FROM SAID PHOTOSENSITIVE ELEMENT UPON DEVELOPMENT ANDPROCESSING OF LATENT IMAGE, SAID RUPTURABLE CONTAINER HOLDING AS APROCESSING LIQUID AT LEAST THICKENING AGENT AND A